(a) Field of the Invention
The present invention relates to a roll-forming system and a method thereof. More particularly, the present invention relates to a roll-forming system and a method thereof that enables both ends of a panel to be formed attractively by roll-forming the panel after cutting grooves are formed at both ends of the panel by using a blanking press.
(b) Description of the Related Art
Generally, twenty to thirty thousand components are sequentially assembled to a vehicle body for manufacturing one vehicle, and particularly, a bumper beam, which is a part of the vehicle body, is assembled to front and rear portions of the vehicle body.
The bumper beam includes an impact-absorbing member for absorbing impact applied from the front or the rear, and a bumper cover covering the impact-absorbing member.
According to a conventional method for manufacturing the bumper beam, two rail members formed by press forming are welded to produce the bumper beam. Recently, a bumper beam has been manufactured by roll-forming a metal plate in order to improve productivity, and such a bumper beam includes a closed cross-section therein so as to absorb impact.
As shown in FIG. 1, a bumper beam 101 of a vehicle includes two closed cross-sections S therein. The bumper beam 101 is manufactured by roll-forming a metal plate to be symmetrical with reference to a middle portion thereof. The roll-forming is sequentially performed along a length direction of the metal plate, and the bumper beam 101 with a predetermined shape is thereby manufactured.
FIG. 2 is a schematic diagram showing a conventional roll-forming system and respective steps of a roll-forming method using the same.
According to the conventional roll-forming system and the roll-forming method by using the same, an uncoiler 201 for uncoiling a coil 200 is provided at a front portion in a process line, and performs an uncoiling step S110.
A straightener 203 for straightening the coil supplied from the uncoiler 201 to be a flat panel 250 is provided at the rear of the uncoiler 201 in the process line, and performs a straightening step S120.
In addition, a brake press 205 is provided at the rear of the straightener 203 in the process line. The brake press 205 performs a boring step S130 by boring a plurality of holes for assembling a main beam in the flat panel 250 supplied from the straightener 203.
A roll former unit 207 including a plurality of roll formers R1, R2, R3, R4, R5, R6, and R7 is provided at the rear of the brake press 205 in the process line. The roll former unit 207 performs a roll-forming step S140 by sequentially bending the flat panel 250 supplied through the uncoiler 201, the straightener 203, and the brake press 205 to be a predetermined-shaped beam.
A round bender 209 including at least one of curvature-forming rolls disposed at both sides thereof is provided at the rear of the roll former unit 207 in the process line. The shaped beam, having gone through the roll-forming step S140, passes through the round bender 209 and is bent to have a predetermined curvature. Thereby, a bending step S150 is performed.
In addition, a cutting press 211 for cutting the shaped beam with a closed cross-section to have a predetermined dimension is provided at the rear of the round bender 209 in the process line, and performs a cutting step S160.
A bumper beam 101 with a predetermined shape shown in FIG. 1 is manufactured by the conventional roll-forming system.
However, since both ends EP of the bumper beam 101 manufactured by the conventional roll-forming system have the same thickness T as the middle portion thereof, interference between the both ends EP of the bumper beam 101 and a bumper cover (not shown) may occur when the bumper beam 101 is assembled to a vehicle body. In addition, it is difficult to have sufficient space for preventing the interference between both ends EP of the bumper beam 101 and the bumper cover (not shown).
To solve such problems, both ends EP of the bumper beam 201 are pressed and the thickness T thereof is reduced so as to have sufficient space between the bumper cover, as shown in FIG. 3. Therefore, design freedom may be heightened and an attractive design of the bumper cover may be achieved.
In order to press the both ends EP of the bumper beam 201, a punch press 213 is provided at the rear of the cutting press 211 in the process line, and performs a forming step S170 of pressing both ends EP of the bumper beam 201 as shown in FIG. 2.
However, since tensile stress is primarily applied to the bumper beam 101 in the roll-forming step, the tensile stress applied to a most-deformed portion P thereof may be larger than a limit tensile stress when the tensile stress is secondarily applied to the both ends EP of the bumper beam 101 in the forming step S170 as shown in FIG. 4. Therefore, a crack or tear may occur at both ends EP of the bumper beam 101.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.